Apparatus for the manufacture of wood fiber panels

ABSTRACT

In an apparatus for the formation on a pervious conveyor band of a cushion of wood fibers entrained by an airstream, the regular distribution of the fibers across the width of the band is effected by a series of longitudinal streamlined depending blades which define adjustable intermediate passages above the band within a vibrating distribution box. The air chest on the perforated upper side of which the band circulates, has its inner space divided into a number of separate chambers connected with at least one suction line through individual valves which permit of distributing the negative pressure below the band in the longitudinal and/or in the transverse direction.

United States Patent APPARATUS FOR THE MANUFACTURE OF WOOD FIBER PANELS6 Claims, 6 Drawing Figs.

US. Cl 302/12, l9/l56.3, 156/370, 156/377 Int. B653 53/04 FieldotSearch302/ll,12, I

Primary Examiner-Andres 1'1. Nielsen Attorney-Alexander and DowellABSTRACT: In an apparatus for the fonnation on a pervious conveyor bandof a cushion of wood fibers entrained by an aiistream, the regulardistribution of the fibers across the width of the band is effected by aseries of longitudinal streamlined depending blades which defineadjustable intermediate passages above the band within a vibratingdistribution box. The air chest on the perforated upper side of whichthe band circulates, has its inner space divided into a number ofseparate chambers connected with at least one suction line throughindividual valves which permit of distributing the negative pressurebelow the band in the longitudinal and/or in the transverse direction.

PATENTEU m 1 l97l APPARATUS FOR THE MANUFACTURE OF WOOD FIBER PANELSBACKGROUND OF THE INVENTION The present invention refers to themanufacture of hard plates or panels of wood fibers by the so-calleddry" process.

The dry process consists in realizing on an appropriate conveyor bandone or several superposed layers of wood fibers which have beenpreviously impregnated with a polymerizable resin and in compressingbetween heated platens the fibrous cushion thus obtained in order tocure the resin which acts as a binder. The panels thus obtained areextremely strong and rigid.

In such a process the characteristics of the panels are largelydependent on the homogeneity of the fibrous cushion and on theuniformity of its thickness. Experience however demonstrates that it isquite difficult to realize these conditions. The fibers .are verygenerally conveyed pneumatically, the conveyor band being realized inthe form of a wire gauze slidably supported by the perforated upper sideof an air chest. The disadvantage of this arrangement is that the edgesof the con veyor band are underfed, the fibrous cushion being less denseand less thick in the corresponding zones. It has been proposed toseparate the defective marginal portions of the fibrous cushion,'thefibers thus eliminated being recycled, but this results in a quiteintricate apparatus and increases the consumption of power. It has alsobeen suggested to combine the pneumatic feed of the fibers with amechanical distribution across the width of the conveyor band, butwithout satisfactory results in actual practice.

Another problem in the dry process resides in the distribution of thenegative pressure along the length of the conveyor band on the airchest. The thickness of the fibrous cushion above the air chestincreases in the advancing direction of the band and therefore thepressure drop in the airstream which passes through this cushionincreases correspondingly. The airflow decreases and therefore thequantity of fibers which settle on the cushion also decreases. It hasbeen proposed to regularize the airflow along the length of the conveyorband by calibrating the perforations of the upper side of the air chestso as to increase their cross section where the fibrous cushion isrelatively thick and to reduce it where this cushion is relatively thin,but the smaller perforations are easily clogged by fine fibers andmoreover the calibrating operation is only effective for the type ofpanel for which it has been effected, another type requiring a differentcalibration.

It is an object of the present invention to provide an ap paratus forthe manufacture of wood fiber panels by the dry process, wherein thethickness of the fibrous cushion to be pressed into a panel, may becontrolled as desired across the width of the cushion, so as to beperfectly uniform, or even reinforced along the edges thereof.

A further object of this invention is to provide an apparatus of thekind above referred to, wherein" the negative pressure which realizesthe fibrous cushion on the conveyor band may be adjusted as desiredalong the length of this cushion, and also across the width thereof, ifrequired.

SUMMARY OF THE INVENTION In accordance with the present invention in anapparatus for the manufacture of wood fiber panels by the dry process,of the kind comprising a pervious conveyor band supported by theperforated upper side of an air chest in which a negative pressure ismaintained, and pneumatic conveying means to The air chest may beinternally divided into a number of chambers in the longitudinal and/orin the transverse direction with respect to the advance of the conveyorband, means being provided whereby the negative pressure may be adjustedas desired in each chamber.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawings:

FIG. 1 is a transverse section of an apparatus according to theinvention for the manufacture of panels of wood fibers.

FIG. 2 is a longitudinal section taken through line II-II of FIG. I. theplane of section of FIG. 1 being indicated by line H.

FIG. 3 reproduces to an enlarged scale a detail of FIG. 2.

FIG. 4 is a section taken along line lV-IV of FIG. 3.

FIG. 5 is a view similar to FIG. 3, but illustrating a slightly modifiedarrangement.

FIG. 6 is a horizontal section taken along line Vl-VI of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus illustrated inFIGS. l and 2 comprises a downwardly-diverging pyramidal inlet chamberor hood I the upper end of which is connected with the conveying conduit2 through which the airstream loaded with wood fibers is supplied to theapparatus. The lower end of chamber 1 opens into a distributing box 3 ofsubstantially rectangular cross section, a highly flexible seal 4 beinginterposed between box 3 and chamber 1 in order to permit the former tovibrate substantially freely. An air chest 5 is disposed below the lowerend of box 3, the horizontal upper side of this air chest being formedwith perforations 5a. A pervious conveyor band 6, as for instance madeof wire gauze, slides on this perforated upper side. For the cleamess ofthe drawing conveyor band 6 has been illustrated in FIGS. l and 2 asslightly spaced from the upper side of chest 5 while it is actually incontact therewith so as to be slidably supported thereby. Band 6 movesfrom right to left in FIG. 2. As shown the vertical walls of air chest 5extend upwardly above the perforated upper side thereof and they areconnected in an airtight manner with the lower edge of the distributingbox 3 by means of another highly flexible seal 7 similar to theabove-mentioned seal 4.

Each of the vertical walls of box 3 which extend transversely withrespect to conveyor band 6 is formed with an elongated horizontal slot3a (FIGS. 1 and 3).

A number of vertical streamlined air-guiding blades 8 are disposedwithin box 3, each being carried by a longitudinal rod 9 the protrudingends of which are passed through slots 3a and carry blocks 10 which aresecured thereto in any appropriate manner, not indicated in FIGS. 2 and3. Each of the transverse walls of box 3 carries a guide formed of twoparallel U-shaped sheet iron members 11 which define a gutter in whichblocks 10 are slidably retained. This gutter is closed by a flat lateralcover 12 which forms a substantially tight seal.

With this arrangement blocks 10, and therefore blades 8, may be disposedat any position desired across the width of the perforated band 6 inorder to determine intermediate air passages of variable cross section.By disposing blades 8 closer to each other above the central portion ofhe band than above the edges thereof, as illustrated in FIG. 1, it ispossible to obtain a uniform distribution of the fibers in the fibrouscushion which issues from the apparatus.

Blocks It) may be fixed at the desired position in any appropriatemanner. In FIGS. 3 and 4 the upper U-shaped member 11 has a series ofholes lla which may selectively receive a screw 13 screwed into eachblock 10. Holes 11a are quite close to each other and those which arenot used may be plugged.

In the modification of FIG. 5 blocks 10 are slidably mounted on a rod 14and each has a setscrew 15, cover 12 being easily removable to permitaccess to screws 15. The ends of rod 14 are appropriately secured toU-shaped members 11.

The air chest 5 is provided with a narrow horizontal inlet 5b (FIG. 2)for the conveyor band 6 and with a corresponding outlet 50 in the formof a rectangular nozzle. The upper side of this nozzle, which has beenillustrated as rigidly secured to the remainder of the air chest ispreferably hingedly supported and may be adjusted at will in accordancewith the thickness of the fibrous cushion A formed of the conveyor band.

Vibrators 16 are secured against the outer side of the lateral walls ofbox 3.

The inner space of the air chest 5 below the perforated upper side 5athereof is divided into eight individual chambers by a transversepartition 5d and by three longitudinal partitions 5e. These chambers areindividually connected to one of two suction lines 17 by valves 18, eachline 17 being in turn connected with a suction fan 19. By appropriatelyadjusting valves 18 it is thus possible to control at will the negativepressure within each chamber and to obtain a uniform fibrous cushionissuing from the apparatus.

The general operation is as follows:

The previous conveyor band 6 advancing in the direction of the arrow inF*G. 2, the air loaded with impregnated wood fibers issuing from theconveying conduit 2 is distributed across the width of suction box 3 byblades 8. If the latter are appropriately adjusted (FIG. 1) the tendencyof the airstream to flow preferentially in the central portion of thewidth of the box may be obviated. if a finer adjustment is required, itmay be'obtained by acting on the valves 18 corresponding to the lateralchambers of the air chest 5. The vibrations imparted to the section box3 prevent the formation of fibrous plugs between the successive blades 8or between the outer' blades 8 and the walls of box 3. As to thedistribution of the wood fibers along the length of the cushion, it maybe controlled by acting on valves 18 so as to increase the negativepressure in the four chambers of air chest 5 which are situated at theleft of transverse partition 5d. The thickness of fibrous cushion A maythus increase regularly between inlet 5b and outlet 5c as this isdesirable for obtaining good results.

As this is conventional in the dry process the cushion formed onconveyor band 6 is thereafter pressed between heated platens.

l claim:

1. An apparatus for use in the manufacture of panels from fibersimpregnated with a binder, comprising:

a longitudinally movable pervious conveyor band;

an air chest having a perforated horizontal upper side in slidingcontact with said conveyor band;

means to maintain a negative pressure within said air chest;

means on said air chest to define above said perforated upper sidethereof a closed space having an inlet and an outlet for said conveyorband;

a plurality of substantially vertical and parallel spaced airguidingblades disposed side-by-side within said closed space at a distanceabove said conveyor band, said blades extending substantiallylongitudinally with respect to said conveyor band and said bladesdefining a plurality of intermediate passages; and means connected tosaid closed space above said blades to supply to said space an airstreamloaded with fibers impregnated with a binder, said airstream beinguniformly distributed by said blades across the width of said conveyorband within said closed space and passing through said band and throughthe perforated upper side of said air chest, while the fibers entrainedby said airstream are retained by said pervious band to form thereon afibrous cushion which may thereafter be pressed into a panel. 2. In anapparatus as claimed in claim 1, said blades being adjustable inposition across the width of saidconveyor band.

3. In an apparatus as claimed in claim 1, said blades having astreamlined cross-sectional profile.

4. In an apparatus as claimed in claim 1, each of said blades having twoends and having at each end a longitudinally protruding rodlikeextension, said means to define a closed space above the perforatedupper side of said air chest comprising two substantially vertical wallsextending transversel with respect to said conveyor band and being eachforme with an elongated horizontal slot, each of said extensions beingpassed through one of said slots, and said apparatus further comprisingmeans exterior to said closed space to adjustably retain said extensionsin position along said slots.

5. In an apparatus as claimed in claim 1, said means to define a closedspace above the perforated horizontal upper side of said air chestcomprising:

longitudinal and transverse walls extending upwardly around said upperside, with said inlet and said outlet being formed in said transversewalls;

an open-ended rectangular distribution box disposed above saidlongitudinal and transverse walls, with said blades being supported bysaid distribution box;

a first flexible seal interposed between said distribution box and saidlongitudinal and transverse walls;

a downwardly diverging hood above said distributing box, said hoodhaving an upper end and a lower end, with said means to supply anairstream loaded with fibers being connected with the upper end of saidhood;

a second flexible seal interposed between said distribution box and thelower end of said hood;

and vibrating means acting on said distribution box to vibrate sametogether with said blades.

6. In an apparatus as claimed in claim 5, said distribution box havingtransverse walls each formed with a horizontal elongated slot, each ofsaid blades having two ends and having at each end a longitudinallyprotruding rodlike extension, each of said extensions being passedthrough one of said slots, and said apparatus further comprising on eachof said transverse walls of said distribution box means exterior to saidbox to adjustably secure said extensions in position across the width ofsaid box and means to substantially prevent airflow through each of saidslots.

1. An apparatus for use in the manufacture of panels from fibersimpregnated with a binder, comprising: a longitudinally movable perviousconveyor band; an air chest having a perforated horizontal upper side insliding contact with said conveyor band; means to maintain a negativepressure within saiD air chest; means on said air chest to define abovesaid perforated upper side thereof a closed space having an inlet and anoutlet for said conveyor band; a plurality of substantially vertical andparallel spaced airguiding blades disposed side-by-side within saidclosed space at a distance above said conveyor band, said bladesextending substantially longitudinally with respect to said conveyorband and said blades defining a plurality of intermediate passages; andmeans connected to said closed space above said blades to supply to saidspace an airstream loaded with fibers impregnated with a binder, saidairstream being uniformly distributed by said blades across the width ofsaid conveyor band within said closed space and passing through saidband and through the perforated upper side of said air chest, while thefibers entrained by said airstream are retained by said pervious band toform thereon a fibrous cushion which may thereafter be pressed into apanel.
 2. In an apparatus as claimed in claim 1, said blades beingadjustable in position across the width of said conveyor band.
 3. In anapparatus as claimed in claim 1, said blades having a streamlinedcross-sectional profile.
 4. In an apparatus as claimed in claim 1, eachof said blades having two ends and having at each end a longitudinallyprotruding rodlike extension, said means to define a closed space abovethe perforated upper side of said air chest comprising two substantiallyvertical walls extending transversely with respect to said conveyor bandand being each formed with an elongated horizontal slot, each of saidextensions being passed through one of said slots, and said apparatusfurther comprising means exterior to said closed space to adjustablyretain said extensions in position along said slots.
 5. In an apparatusas claimed in claim 1, said means to define a closed space above theperforated horizontal upper side of said air chest comprising:longitudinal and transverse walls extending upwardly around said upperside, with said inlet and said outlet being formed in said transversewalls; an open-ended rectangular distribution box disposed above saidlongitudinal and transverse walls, with said blades being supported bysaid distribution box; a first flexible seal interposed between saiddistribution box and said longitudinal and transverse walls; adownwardly diverging hood above said distributing box, said hood havingan upper end and a lower end, with said means to supply an airstreamloaded with fibers being connected with the upper end of said hood; asecond flexible seal interposed between said distribution box and thelower end of said hood; and vibrating means acting on said distributionbox to vibrate same together with said blades.
 6. In an apparatus asclaimed in claim 5, said distribution box having transverse walls eachformed with a horizontal elongated slot, each of said blades having twoends and having at each end a longitudinally protruding rodlikeextension, each of said extensions being passed through one of saidslots, and said apparatus further comprising on each of said transversewalls of said distribution box means exterior to said box to adjustablysecure said extensions in position across the width of said box andmeans to substantially prevent airflow through each of said slots.